Hi Goucheng,

you have some options to solve the problem:


First option:    - You always can do the master SU-8 in a negative way, simply
inverting the mask design (use a negative of your normal mask)

                       In this way you get a right SU-8 master, so a simple
soft-litho will give you the right PDMS replica.


Second option:- What if you cannot get a negative mask?? You simply will need a
few more steps:

                       1-Use your normal mask and get the normal SU-8 master.

                       2-Soft-litho: to obtain the inverse PDMS replica.

                       3-Use the PDMS replica as a mold and pour fresh SU-8 on
it, then cure it with UV

                       4-Peel the SU-8 replica, this is the right replica- the
same result you will get with a inverse mask. (Peeling should be easy, due to
you have a PDMS stamp)

                       5-Soft-litho of the SU-8 replica to obtain your desired
PDMS estructure... and you do it.

it works fine to me.

Regards

Eowin